The long term goal of the proposed research is to understand the role of the B- amyloid precursor protein (APP) trafficking in the pathogenesis of Alzheimer's disease. Recent studies have established that APP is an itinerant membrane protein which displays multiple cytoplasmic sorting signals. The cytoplasm tail of APP contains a sequence GYENPTY related to the 6-residue LDLR internalization signal FDNPVY as well as the segment YTSI which conforms the 4-residue tyrosine-based internalization consensus sequence. These signals are recognized by molecular sorting machinery located at different sites within the cell and determine the intracellular trafficking pathways along which APP is routed. Although there is evidence that AB can be generated from APP expressed on the cell surface and that internalization is required, it is unclear whether this is the exclusive or even the major trafficking pathway leading to the production of AB. The primary objectives of the present application are to determine how trafficking of APP influences AB production and whether APP trafficking is regulated by other gene products implicated in the pathogenesis of AD. To accomplish these goals, the PI will take advantage of emerging conceptual and methodological advances in the field of membrane protein sorting and apply them to APP trafficking. The major experimental approach will be to exploit transferrin receptor (TR) chimers including APP-TR chimera that all quantitative biochemical and morphological studies of membrane proteins to performed. The use of the TR chimeras allows unique properties of this receptor-ligand system to be used to define membrane protein trafficking under a variety of experimental conditions. The methods developed to modify protein trafficking through the study of TR chimeras will be used to determine how altered APP trafficking affects AB production.